There are several types of
electrical switching products. From low cost to high performance, each method
serves a part of the market.

Solid state relays
(SSR): The SSR products are usually packaged in the familiar cube shape
and are frequently referred to as "hockey puck relays". SSRs can use internal
triacs, or the better SSRs will use internal SCRs (a pair of Silicon
Controlled Recifiers). Power-io only uses internal SCRs. SSRs
turn on and off at the zero crossing mark on a sine wave so electrical surges
and noise spikes are greatly reduced. Since there are no moving parts in a SSR,
they can be cycled on and off many times per second. SSRs can be an ideal
product if you pay attention to the three important application items. Those
are: avoid over voltage (surges), over current, and over temperature. For
further information, visit:
Solid
state relay -- extended life and optimum performance.

Power-io
has designed several unique features into our SSR family as part of our Maximum
Surge Survival technology. An ideal cycle time for a SSR is often as fast
as 0.2 - 2 seconds and virtually an unlimited number of cycles. SSRs are used
frequently for industrial control of resistive heaters, motor starters (due to
excellent short term amperage surge capability), PC based control applications
(due to minimum control signal input requirements), on/off lighting
applications (zero crossing extends the life of the lamp) and other general
purpose switching applications. When used for heater control, the fast on/off
cycles provide excellent temperature control and this dramatically improves the
heater life due to a reduction in thermal shock. For example: at 20% heater
demand, this may mean 0.05 seconds on, 0.15 seconds off, 0.05 on, .... This is
actually 3 sine waves on, 9 sine waves off, 3 on, 9 off, .... Since you are
switching full sine waves, starting at the zero crossing mark and ending at the
zero crossing mark, there is no noise generated and the power is permitted to
start at zero and then ramp up. The heater stabilizes at a temperature range
and does not fluctuate, thus reducing thermal stress and, therefore, increasing
the heater's life. For information on Power-IO's SSR products, please visit the
"H" hockey puck products at: solid state relay
products

Solid state contactors
(SSC): When an industrially hardened SSR is assembled onto a properly
sized heat sink, the final product is frequently called a solid state
contactor. Power-IO uses over-sized internal SCRs (often 20-100% oversized), on
a DCB (Direct Copper Bonded ceramic/copper assembly) attached to a thermally
optimized heat sink design, finger-safe screw terminations, and an universal
mounting bracket. Installation size is minimized by our industry-leading
capability that permits you to install the product with NO spaces between
products on the same din rail. Therefore, the Power-IO "D" din rail family
offers the smallest installed product in the industry. As a finished contactor,
the product provides the fastest and most convenient way to install a complete
solid state switching product. For more information, please visit:
solid-state
relays

For electric heater control, solid
state contactors are typically used with PLCs, PCs, network I/O, or PID
controllers that generate the on/off pulsing VAC or VDC control signal. This
may be called a time proportional output, TPO, or PWM pulse wave modulation.
When used with some PLCs, it may be easier to reduce programming time by using
an analog output so Power-IO also has solid state contactors that accept a
4-20mA analog control signal that then gets converted into the appropriate zero
crossing output. (4mA=off, 12mA=50%, 16.8mA=80%. 20mA=full on). These have a
part number starting with DMA (Din rail, Milliamp input,
AC switching). Visit: 4-20 mA input single phase or three
phase solid state relays

"Intelligent" solid state
contactor: The solid state contactors can have additional functions
added for diagnostics. The "C Family" contactors have the ability to create an
output based upon: SCR problems, load open, fuse open, and thermal problems. In
addition, they have the Power-io exclusive feature of monitoring the SCR's
health status independent of the control input which is beneficial during
machine start-ups. Intelligent contactors are one of the fastest growing
segments of power control since they integrate into larger installations,
un-staffed applications, and remote monitored applications for on/off power
control or on/off motor control. More information is at
C Family intelligent
solid state contactors.

This intelligent model has 3
control input selections:

Two independent 4-32 VDC inputs
for normal ON/OFF/ON/OFF control.

One 0-10 VDC analog input for
easy PLC programming. For example: the customer supplies a 2 VDC input = 20% =
0.2 seconds ON, 0.8 seconds OFF, 0.2 ON, 0.8 OFF. The contactor calculates the
ON/OFF ratio to match the analog signal, based upon a one second overall time
period.

"Zero Crossing" Silicon
Controlled Recifier (SCR): The Power-IO solid state relays and solid
state contactors use internal zero crossing silicon controlled rectifiers and
are sometimes called SCR products, SCR power controllers, SCR power packs, or
thyristors. The exclusive way that we activate and deactivate the zero crossing
is extremely precise, leading to an exceptionally clean, noise free control
mode. When activated by a VAC control signal, we typically do NOT need burden
resistors on the control input. Power-IO products are usually for applications
from 1-100 amps. There are other SCR vendors who concentrate in SCR
applications up to 5000 amps.

"Phase Angle" Silicon
Controlled Recifier (SCR): A minority of the heater applications use
transformer coupled loads or low cold resistance loads. Your heater
manufacturer will point out that these loads (such as certain silicon carbide
heaters or moly disilicide heaters) require phase angle SCR control plus
current limiting, automatic recalculation and correction for voltage
fluctuations, partial load imbalance, and/or other features. These units are
typically much more expensive but may be required for applications such as
molecular beam epitaxy equipment in semi-conductor fab facilities. Phase angle
control means the the electrical power is on for part of each sine wave. This
permits precise control, but chopping every sine wave creates electrical noise
that may impact nearby equipment. For European applications or any country
where CE regulations are used, phase angle power controllers usually require
customized noise filters that may be as expensive as the phase angle controller
that they are attached to.

Mosfet Solid State
Relay: When switching DC loads, the internal device inside the solid
state relay is a mosfet semiconductor (up to 200 VDC) or IGBT (up to 900 VDC).
Power-io has a unique technology that permits the rapid 15 Khz switching times
for 0-200 VDC applications. Rapid switching is required for PWM dc servo
control, automated test equipment applications, and other applications where
the need is for instantaneous ON or OFF control. Mosfet solid state relays are
also used for DC applications in order to avoid contact bounce or other
mechanical problems that are associated with electro-mechanical relays. Most dc
loads are somewhat inductive, so it is recommended that you install a diode
across the load to avoid EMF problems. For more information visit:
mosfet solid state
relays

Mosfet Solid State
Relay: In 2010, the DC switching solid state relays were expanded to
include the HDD-E family. The "E" expansions included: faster speeds up to 20
kHz PWM, lighter weight for vehicle or airborne applications, and cooler
performance for a decrease in heat sink requirements. For more information
visit: mosfet solid state
relays

Insulated Gate Bipolar
Transistor (IGBT): For DC applications from 0-900 VDC, the Power-io
HDD-6V15, HDD-6V20E and HDD-9V30E are off-the-shelf IGBT units with our
exclusive fast turn ON/OFF/ON/OFF gating control circuit. They are used for DC
switching applications up to 900 VDC. These are frequently used for solar
applications for DC load control, solar panel disconnect, or battery/dump load
toggle selection. For information, please visit:
IGBT solid state
relays

Other non solid state products
include (not sold by Power-io):

Mechanical relays or
mechanical contactors: The cost of a mechanical relay or mechanical
contactor is influenced by amperage and usage. As these increase, so does the
price. A mechanical product typically has two ratings: the number of mechanical
cycles (a high number) and the number of electrical cycles (a low number).
Therefore, mechanical products should be used when the final device is
activated infrequently. Mechanical relays are seldom used for heater
applications since the cycle time is too slow and the overall product life is
often too short. A mechanical device turns on or off when the coil is energized
which can result in noise spikes or surges since this is not at the zero
crossing point. An ideal cycle time for a mechanical device is often 30-120
seconds or more; and a total on/off cycle life of 50,000 - 250,000 cycles. Some
applications (PLC controlled, PC controlled, or sharing the powerline with
other nearby computers) will require snubbers across the control terminals to
help to suppress the frequent voltage surges upon opening.

Mercury contactors or mercury
displacement relays (MDR): A mercury contactor uses a pool of mercury,
inside a glass sealed tube, to electrically connect the two contacts. This pool
may be more than 100 grams of mercury for a single contactor. Since mercury is
a cancer causing agent and is banned in many states, countries, or industries;
there are restrictions on shipping, storing, or cleaning up if a contactor
should leak or explode. A mercury contactor is not a zero crossing device so
there will be noise spikes or surges that may affect nearby electrical products
or PLCs. An ideal on/off cycle time for a mercury contactor is often 10-20
seconds and 3-8 million overall cycles. Mercury contactors were used frequently
for industrial heater control of resistive heaters in the years from 1960 to
2000. When used 24 hours a day in a heater application, there may be 3 million
on/off cycles in a single year. Therefore, the mercury contactors might be
replaced many times during the life of the machine. Information about the
legally
required elimination of mercury contactors is online at several locations.
Worldwide elimination of mercury is being required by state laws, food
industries, environmentalist groups, and more.